OBJECTIVES: To characterize the behavior of ribosomal particles in a non-growing cell population in which the rate of protein synthesis is maintained at low levels; to correlate such behavior with the limitation in protein synthesis so as to understand the mode of translational control employed by the cell in adjusting protein synthesis to growth and metabolic activities; to determine the regulatory steps which are operative in the enhancement of protein synthesis associated with the onset of cell growth; to relate modifications of the cell membrane with biochemical alterations regulating nuclear and cytoplasmic functions as they participate in control of cell proliferation; to detect and characterize the biochemical steps which control protein synthesis during the physiological cessation of cell growth and division.